The invention relates to a data bus for a plurality of nodes that are connected to one another via a star coupler. Such a data bus is known from the unpublished German patent application 19720401. Herein, the nodes are connected to the data bus via transmitter/sender modules as long as nodes are operating properly bus nodes are active even when they are not required. Depending on the type of application, however, deactivation of the entire data bus may not always be desirable. After a vehicle is turned off, nodes serving the access control and antitheft protection systems should remain active even though all the rest of the nodes are not required.
The object of the invention is to provide a data bus of the aforementioned type that allows nodes to be selectively disconnected.
According to the present invention, a series of individual measures in combination provide the desired effect. In one of such measures, optionally occurring optical signals are converted to electrical signals and fed as input signals to the star coupler arrangement. The star coupler arrangement itself includes a logical decision gate to which input signals are fed, whose. output is connected to the inputs of the nodes in a parallel manner via an electrical line. A switch is arranged in parallel at least at the inputs of the nodes, Which are disconnected when required. The switch can optionally be activated, and interrupts the transmission segment between said decision gate and said node, thus disconnecting said node from the data bus.
In an advantageous development of the invention the addressability of the switch enables only a single node to be disconnected from the data bus, if required, in a simple manner.
Finally, such a switch can be assigned to a group of nodes, which can always be connected or disconnected as a unit.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.